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Smells Unit – Investigation IV Polar Bears and Penguins.

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Presentation on theme: "Smells Unit – Investigation IV Polar Bears and Penguins."— Presentation transcript:

1 Smells Unit – Investigation IV Polar Bears and Penguins

2 © 2004 Key Curriculum Press. Unit 2 Investigation IV Admit Slip Consider the following illustration: (cont.) Draw the Lewis dot structure for HCl. If the penguin represents a hydrogen atom and the polar bear represents a chlorine atom, what does the ice cream represent in the drawing? What do you think the picture is trying to illustrate?

3 © 2004 Key Curriculum Press. Unit 2 Investigation IV Agenda Admit Slip Comic Book Questions Notes Exit Slip Product: Questions, Notes, Exit Slip Homework: Draw picture

4 © 2004 Key Curriculum Press. Unit 2 Investigation IV You will be able to: Recognize and explain a polar bond.

5 © 2004 Key Curriculum Press. Unit 2 Investigation IV Activity Purpose: In this lesson you will be exploring polarity and bonding between atoms in greater detail. A comic book will provide new information about these topics and will introduce you to the concept of electronegativity, which helps us to understand partial charges.

6 © 2004 Key Curriculum Press. Classwork : Complete questions Classwork is due at: Unit 2 Investigation IV

7 © 2004 Key Curriculum Press. Unit 2 Investigation IV Making Sense What does electronegativity have to do with polarity?

8 © 2004 Key Curriculum Press. Unit 2 Investigation IV The tendency of an atom to attract electrons shared between two atoms is called electronegativity. The most electronegative atoms are in the top right of the periodic table. The least electronegative are in the bottom left. An atom that strongly attracts the shared electrons is considered highly electronegative and ends up with a partial negative charge on it. The atom with lower electronegativity will end up with a partial positive charge on it.. Electronegativity/Polarity1/4/11

9 © 2004 Key Curriculum Press. Unit 2 Investigation IV In a nonpolar covalent bond, the atoms have equal electronegativity and share electrons equally. If the electronegativities between two atoms are even slightly different, they form what is called a polar covalent bond. They atoms share electrons unequally. When the electronegativities between two atoms are greatly different, they form an ionic bond. In an ionic bond, one atom (a metal) completely gives it’s electron(s) to the other atom (a nonmetal).

10 © 2004 Key Curriculum Press. Unit 2 Investigation IV The word dipole (which means two poles) is used to describe a polar bond or a polar molecule. A molecule is polar if the ends of the molecule have two different charges. A molecule can have polar bonds but not be a polar molecule overall. (cont.)

11 © 2004 Key Curriculum Press. Unit 2 Investigation IV This picture shows how to illustrate a polar bond. The crossed end of the arrow indicates the positive (+) end of the polar bond and the arrow points in the direction of the negative (-) end   Notes (cont.)

12 © 2004 Key Curriculum Press. Unit 2 Investigation IV The more electronegative atom has the partial negative charge. The less electronegative atom has the partial positive charge. You also add the Greek symbols to show these charges.  

13 © 2004 Key Curriculum Press. Unit 2 Investigation IV Notes (cont.)

14 © 2004 Key Curriculum Press. Unit 2 Investigation IV Exit Slip Is the bond between these atoms polar? Explain your reasoning. How would the atoms be portrayed in the comic book—as polar bears, penguins, or both? Explain.

15 © 2004 Key Curriculum Press. Unit 2 Investigation IV Wrap-Up Anytime there are two different types of atoms sharing electrons, there will be a partial negative charge on one atom and a partial positive charge on the other atom. Electronegativity measures the tendency of an atom to attract the electrons in a bond. (cont.)

16 © 2004 Key Curriculum Press. Unit 2 Investigation IV The bonds are labeled nonpolar covalent, polar covalent, and ionic as the difference in electronegativity between the two atoms in the bond increases. (cont.)


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